The need to prevent health care workers from being injured by used needles is well recognized. One type of safety syringe allows the needle to be retracted into the barrel for disposal. See, for example, U.S. Pat. No. 4,507,117 to Vining, et al., U.S. Pat. No. 4,826,489 to Haber, et al. and U.S. Pat. No. 5,122,118 to Haber, et al.
One of the problems with conventionally designed safety syringes in which the needle is withdrawn into the barrel for safe disposal, is cost. That is, conventional designs, although perhaps effective, may be too costly to find widespread use as disposable syringes. Also, many safety syringes require the user to use the syringe differently than conventional syringes. This can also provide a disincentive to use the safety syringe.